Method of and apparatus for fumigating



June 26, 1928. 1,675,123

F. J. METZGER ET AL METHOD OF AND {\PPAHA'I'US FOR F'UMIGATING Filed Oct. 23, 1926 y? lNgNTOL 6am @ZM -AMMZM ATTORNEY Patented 1......26, 1928.

UNITED STATES PATENTv OFFICE.

FLOYD I. KETZGER, OF NEW YORK, N. Y., AND GEORGE CARL BAUER, 01 L08 GELES, CALIFORNIA, ABSIGNORB TO CALIFORNIA CYANIDE COMPANY, INCORPORATED, NEW YOBKQN. Y., A CORPORATION OF DELAWARE.

METHOD OF AND APPARATUS FOR FUMIGATING.

Application filed October 23, 1928. aerial No. 148,592.

This invention relates to fumigation and particularly to a method of and a paratus for generati and applying hy rocyanic acid gas for fiie purpose of destroying inc sects and other pests.

Liquid hydrocyanic acid has been used heretofore as a fumigant and is a very satisfactory medium for that purpose. t may be evaporated within the enclosure which is 10 to be fumigated or converted into the aseous phase outside the enclosure to whi the gaseous hydrocyanic acid may be delivered through a suitable pipe. The use of liquid hydrocyanic acid has certain disadvantages l owin to the nature of the material. The

liqui must be transported in sealed containers capable of withstanding pressure and it tends to deteriorate and has been known to decompose with explosive force.

uid with great care.

Calcium 0 anide, on the other hand, is a solid and fairly stable product except when exposed to the atmosphere in the presence of 2 moisture. When so ex sed the calcium cyanide decomposes readi y and releases practically all of its cyanide content in the form of gaseous hydrocyanic acid. It may, however, be stored indefinitely in ordinary sealed containers and it can be transported and utilized without any particular hazard. 2 Calcium cyanide can be a plied for fumigation purposes by introducing it either as a ust cloud or simply as an ex osed layer to the space to be fumigated. e use of calcium cyanide in this manner, while satisfactory in many situations, has the disadvantage that the solid material remainin after the hydrocyanic acid has been release and consisting substantiall of calcium hydroxide is not always e y removed from the space and may remain as an unsightly coating t(:pon objects within the space to be fumi It l s the object of the (present invention to provide a method of an apparatus for generating and applying hydroc anic acid gas in which solid cium cyani e is employed.

Other objects and advanta of the invention will be apparent as it is better underby reference to he llowin specifi- It is necesary, therefore, to handle the liq-- cation and the accompanying drawing in which the figure illustrates diagrammatically a suitable type of apparatus for the practice of the invention.

In carrying out the invention the solid calcium cyanide in finely divided form ma be placed upon any suitable filter medium which will retain the powder and permit the passage of a gaseous medium such as air. Suitable filter media are crushed rock, steel wool, excelsior and the like. Furthermore, a cloth bag or a diaphragm composed of cloth will retain the dust satisfactorily, permitting the gaseous mixture containing hydracyanic acid to pass therethrough. The gas containing hydrocyanic acid is delivered to the space to be fumigated and after serving its purpose it may be dischar to the atmosphere or returned by a sui ta le circulating means to the generator to a ain take up a quantity of hydrocyanic aci for use in the space to be fumigated.

To ensure the proper generation of hydrocyanic acid it is necessary that a. small amount of moisture be present in the air or other gas which contacts with the calcium cyanide. At ordinary atmospheric temperatures, particularly those prevailing in summer, together with normally high relative humidity, there is sufficient moisture in the air to decompose calcium cyanide with sufiicient rapidity for the purpose of the invention unless for any reason abnormally high hydrocyanic acid concentrations are required or the time permitted for the fumigation is limited. In cold winter weather and under atmospheric conditions of low relative humidity it may be necessary or desirable to artificially humidify the air or other as emplo ed, and for this urpose a" sui 1e humi 'fier may be' provided to ensure the saturation of the air or other gas which is delivered to the generator.

In the practice of the invention we first determine the cubic contents of the space to be fumigated and from this we ascertain the amount of hydrocyanic acid and consequently the amount of calcium cyanide which must be utilized to complete the fumi tion, basing the calculation upon well rown standards of the required concentration of hydrocyanic acid for the purpose of killing the particular pest or pests which exist within the enclosure to be fumigated. The pre determined quantity of calcium c anide is placed then upon the filter and t e air or other gas containing the requisite proportion of moisture is blown through the filter. The

resulting gaseous mixture containing hydrocyanic acid is delivered to the enclosure to be fumigated and may, if desired, be returned through a suitable circulating apparatus to the generator. If the gas is c1rcu lated, moisture may be added thereto before the gas again comes into contact with the calcium cyanide.

In the preferred form of apparatus for the practice of the invention a generating chamber is employed in which the air or other gas circulates upwardly toward a filter which is disposed near the to of the chamher so that only a portion the solid calcium cyanide or the residue therefrom reaches the filter. The solid calcium cyanide is fed to the chamber .near the bottom thereof and the upward flow of the gas within the chamber causes a suspension of the fine particles of calcium cyanide and a resulting rapid generation of hydrocyanic acid. The filter at the top of the chamber separates the solid material from the gaseous stream which continues through the filter and through a suitable pipe to the enclosure' to be fumigated'. return pipe from the enclosure may deliver the gas to a circulating pump and the latter may return it through a humidifier,-if the addition of moisture is necessary, and thence to the chamber for the generation of additional 'quantities of hydrocyanic acid. Preferably, although not necessarily, the solid calcium cyanide is fed gradually to the generating chamber while the generation and fumigation is proceeding. A suitable trap may be provided to facilitate the withdrawal of the spent material from the generating chamber after one or more fumigations have been conducted. The time during which .the apparatus may remain in use without dismantling and cleaning of the filter may thus be prolonged.

Referring to the drawing which illustrates the preferred embodiment of the apparatus, 5 indicates a generating chamber at the upper end of which a filter bed 6 is provided. The filter bed may be composed of a diaphragm 7 of cloth or other suitable material and a-layer 8 of steel wool. excelsior or the like; disposed thereon. The solid calcium cyanide is placed in a hopper 9 and may be delivered to the generating chamber by a screw 10 or other feeding device actuated mechanically as, for example. through a 2 gear 11 connected to a shaft 12 which supports the screw. The air or other gas enters the bottom of the generating chamber 5 through a pipe 13 and an inlet 14. The latter should be so proportioned with reference to the volume of gas admitted to the generating chamber as to ensure a velocity sufiicieut to maintain the solid calcium cyanide and the residue therefrom in suspension during the generating period. A pipe 15 is connected to the top of the generating chamber above the filter 6 and conveys the gaseous mixture containing hydrocyanic acid to a chamber or other enclosure 16 which is to be fumigated. The chamber 16 may be a rigid structure to which articles to he fumigated may be introduced or a tent or other enclosure adapted to he placed about the stationary objects.

Since circulation of the gas is desirable a return pipe 17 is connected to the enclosure 16 and to a circulating pump 18 of any suit able kind. The latter delivers the gas through a pipe 19 to a humidifier 20 which may comprise a simple chamber having a partition 21 and a filling 22 of any suitable material designed to ensure maximum con tact between the gas and the water which is delivered through a pipe 23 at the top of the humidifier. A sealed overflow 24 is provided at the bottom of the humidifier to facilitate the escape of surplus water. The humidified gas is delivered through a pipe 25 to the pipe 13 and passes thence through the inlet 14 to the generating chamber. A trap 26 in the bottom of the pipe 13 permits the withdrawal of spent material from the'generating chamber.

In the use of the apparatus as described water is permitted to enter the humidifier and the circulating pump is started to cause a circulation of air through the system. The feeding device is then "permitted to deliver calcium cyanide from the hopper to the generating chamber. The rate of feeding does not affect the generation materially and it is possible to secure satisfactory re sults by delivering the complete charge of calcium 0 anide immediately to the generating cham er. We prefer, however, to feed the calcium cyanide at a reasonably slow rate during the early part of the fumigating eriod. When all of the solid calcium cyanide has been introduced to the chamber circulation is continued until substantially all of the cyanogen in the solid material has been released in the form of hydrocyanic acid and utilized for its intended purpose.

As an illustration of the application of the invention a box car which required fumigation was laced within a tight compartment built or the purpose which contained 9.426 cubic feet of gross air space. A suitable concentration of hydrocyanic acid for this space was known to be .4% by volume as determined from previous experience. Five pounds of calcium cyanide containing 2.84 pounds of cyanogen were placed in the feed hopper and the circulating pump was started and was found to be circulating 347 cubic feet of air per minute through the entire apparatus including the compartment enclosin the box car. The calcium cyanide was then fed 'at an approximately uniform rate during a period of five minutes. After the predetermined amount of calcium cyanide had been fed'to the generator the operation of the pump was continued for a further period of fifteen minutes in order to stir u the air within and around the box car an to secure an approximately equal distribution of hydrocyanic acid throughout the chamber enclosing it. At the end of this time the concentration of hydrocyanic acid within the compartment was found by analysis to be 403% by vol- -ume.

The residue remaining in the generating chamber was removed and was found to weigh 0.625 pounds. The residue in the filter was found to weigh 2.37 unds. The total amount of c anogen in th residues calculated from t e analysis of each was .082 pounds. The efliciency of hydrocyanic acid generation, based on the cyanogen in the calcium cyanide emfployed, was 97.1%.

It is possible, there ore, in carrying out the invention to secure the evolution of more than 90% of the cyanogen content of the calcium cyanide used in the form of hydroc anic acid. No dust can be perceived in t e stream of air or other gas entering the space to be fumigated and consequently the materials undergoing fumigation are protected adequately from injuri by the solid material therewit No. subsequent cleaning of the fumigated space is necessary.

Among the advantages of the invention are the safety and ease with which the highl poisonous hydrocyanic acid may be hand ed and applied in the manner herein described. The solid calcium cyanide can be delivered from sealed containers directly to the hopper without any substantial escape of hydrocyanic acid. Thereafter the hydrocyanic acid is generated in a closed chamber and is delivered directly to the space to be fumigated and is applied therein without danger to the operators who handle the apparatus.

Various chan es may be made in the procedure as described as well as in the apparatus employed without departing from the invention or sacrificing the advantages thereof.

We claim:

1. The method of fumigating which comprises subjecting a solid cyanide-containing material to the action of a moist gaseous medium capable of causing evolution of hydrocyanic acid from the solid materiahdelivering the gaseous medium containing the contact ofthe hydrocyanic acid to the space to be fumi gated.

3. The method of fumigating, which comprises subjecting a solid cyanide-containing material to the action of a moist gaseous medium capabe of causing evolution of hy-. drocyanic acid from the solid material, delivering the gaseous medium containing the hydrocyanic acid to the space to be fumiated, withdrawing the gaseous medium iron! the space to be fumigated, adding moisture thereto and returning it for further contact with the solid material.

4. The method of fumigating, which comprises subjecting a solid material containin calcium cyanide to the action of moistened air and deliverin the air containing hydroc anic acid pro uced by decomposition of the cialcium cyanide to the space to be fumiate g 5. The method of fumigating, which comprises subjecting a solid material containing calcium cyanide to the action of moist air, deliverin the air containin hydrocyanic acid pro uced by decomposition of the calcium cyanide to the space to be fumigated, withdrawing and moistening the air and returning it for further contact with the solid material.

6. The method of fumigating, which com- Er'ises circulating a moist gaseous medium tween a space to be fumigated and a body of solid cyanide-containing material capable of decomposing upon contact with the gaseous medium to produce hydrocyanic acid.

7. The method of fumigating, which com prises circulating a moist gaseous medium between a space to be fumigated and a body of solid cyanide-containing material capable of decomposing upon contact with the gaseous medium to produce hydrocyanic acid and moistening t e gaseous medium before contact thereof with the solid material.

8. The method of fumigating, which comprises passin a moist gaseous medium through a bed of solid cyanide-containing material capab e of decomposing'in the presence of the gaseous medium to produce hydrocyanic acid and delivering the gaseous medium containing the hydrocyanic acid to the space to be fumigated.

9. The method of fumigating, which oomprises passin a moist gaseous medium through a bof of solid cyanide-containing material capab e of decomposing in the presence of the gaseous medium to produce hydrocyanic acid, delivering the gaseous medium containing the h drocyanic acid to the space to be fumigate withdrawin the gaseous medium from the space to be umigated and returning it for further contact with-the solid material.

10. The method of fumigating, which comprises passing a moist gaseous medium through a body of solid cyanide-containing material capable of decomposing in the presence of the gaseous medium to produce hydrocyanic acid, delivering the gaseous medium containing the h drocyanic acid to the space to be fumigate withdrawing the gas eous medium from the space to be fumigated, adding moisture thereto and returning it for further contact with the solid material.

11. The method of fumigating, which comprises passing moist air through a body of soli material containing calcium cyanide and delivering the air containing hydro cyanie acid produced by decomposition of the cyanide to the space to be fumigated.

12. The method of fumigating, which comprises passing moist air through a body of solid material containing calcium cyanide, deliverin the air containing hydrocyanic acid pr need by decomposition of the cyanide to the space to be fumigated, withdrawing the air from the space to be fumigated and returning it for further contact with the solid material.

13. The method of fumi ating, which comprises passin moist air rough a body of solid materia containing calcium cyanide, delivering the air containing hydrocyanic acid produced by decomposition of the cyahide to the space to be fumigated, withdrawing and moistening the air and returning it for further contact with the solid material. 14. In anapparatus for fumigating. a chamber. means at one end of the chamber to permit the passage of a gaseous medium and to retain solid particles, means for delivering a gaseous medium thereto, an enclosure to be fumigated, means for the space to be fumigated and means for delivering the gaseous medium to the enclosure.

15. In an apparatus for fumigating, a chamber, means therein to permit the passage of a gaseous medium and to retain solid particles, means for feeding solid material to the chamber, means for delivering a gaseous medium thereto, an enclosure for the space to be fumigated and means for delivering the gaseous medium to the enclosure.

16. In an apparatus for fumigating, a chamber, means therein to permit the passage of a gaseous medium and to retain solid particles, means for delivering a gaseous medium thereto, an enclosure for the space to be fumigated, means for delivering the gaseous medium to the enclosure and means for returning the gaseous medium to the chamber.

17. In an apparatus for fumigating, a chamber, means therein to permit the passage of a gaseous medium and to retain solid particles. means for deliverin a gaseous medium thereto. an enclosure or the space for delivering the gaseous medium to the enclosure and means for returning the gaseous medium to the chamber, including means for maintaining circulation of the gaseous medium.

18. In an apparatus for fumigating, a chamber, means therein to permit the passage of a gaseous medium and to retain solid. particles, means for deliverin a gaseous medium thereto, an enclosure or the space to be fumigated, means for delivering the gaseous medium to the enclosure, and means for returning the gaseous medium to the chamber, including means for maintaining circulation of the gaseous medium and means for moistening the gaseous medium.

In testimony whereof we afiix our signatures.

FLOYD J. METZGER. GEORGE CARL BAUER.

CERTIFICATE OF CORRECTION.

Patent No. 1, 675.123.

Granted June 26, 1928. to

FLOYD J. METZGER ET AL.

It is hereby certified that error appears in the printed specification of the b 0116 numbered patent requiring correction as follows: mlsspelled word "hydracyanic" read "hydrocyanic";

Page 1, line 66, for the page 3', line 80, claim 3, for

Z'capahe" read "capable"; page 4, line 44, claim 14, before the word "means" insert the words and comma "means for introducing solid material to the chamhcr,"; and that the said Letters Patent should he read with these corrections therein that the same may conform to the record. of the case in the Patent Office.

Signed and sealed this 21st day of August, A. D. 1928.

M. J. Moore, Acting Commissioner of lfatents.

drocyanic acid, delivering the gaseous medium containing the h drocyanic acid to the space to be fumigate withdrawin the gaseous medium from the space to be umigated and returning it for further contact with-the solid material.

10. The method of fumigating, which comprises passing a moist gaseous medium through a body of solid cyanide-containing material capable of decomposing in the presence of the gaseous medium to produce hydrocyanic acid, delivering the gaseous medium containing the h drocyanic acid to the space to be fumigate withdrawing the gas eous medium from the space to be fumigated, adding moisture thereto and returning it for further contact with the solid material.

11. The method of fumigating, which comprises passing moist air through a body of soli material containing calcium cyanide and delivering the air containing hydro cyanie acid produced by decomposition of the cyanide to the space to be fumigated.

12. The method of fumigating, which comprises passing moist air through a body of solid material containing calcium cyanide, deliverin the air containing hydrocyanic acid pr need by decomposition of the cyanide to the space to be fumigated, withdrawing the air from the space to be fumigated and returning it for further contact with the solid material.

13. The method of fumi ating, which comprises passin moist air rough a body of solid materia containing calcium cyanide, delivering the air containing hydrocyanic acid produced by decomposition of the cyahide to the space to be fumigated, withdrawing and moistening the air and returning it for further contact with the solid material. 14. In anapparatus for fumigating. a chamber. means at one end of the chamber to permit the passage of a gaseous medium and to retain solid particles, means for delivering a gaseous medium thereto, an enclosure to be fumigated, means for the space to be fumigated and means for delivering the gaseous medium to the enclosure.

15. In an apparatus for fumigating, a chamber, means therein to permit the passage of a gaseous medium and to retain solid particles, means for feeding solid material to the chamber, means for delivering a gaseous medium thereto, an enclosure for the space to be fumigated and means for delivering the gaseous medium to the enclosure.

16. In an apparatus for fumigating, a chamber, means therein to permit the passage of a gaseous medium and to retain solid articles, means for delivering a gaseous medium thereto, an enclosure for the space to be fumigated, means for delivering the gaseous medium to the enclosure and means for returning the gaseous medium to the chamber.

17. In an apparatus for fumigating, a chamber, means therein to permit the passage of a gaseous medium and to retain solid particles. means for deliverin a gaseous medium thereto. an enclosure or the space for delivering the gaseous medium to the enclosure and means for returning the gaseous medium to the chamber, including means for maintaining circulation of the gaseous medium.

18. In an apparatus for fumigating, a chamber, means therein to permit the passage of a gaseous medium and to retain solid. particles, means for deliverin a gaseous medium thereto, an enclosure or the space to be fumigated, means for delivering the gaseous medium to the enclosure, and means for returning the gaseous medium to the chamber, including means for maintaining circulation of the gaseous medium and means for moistening the gaseous medium.

In testimony whereof we afiix our signatures.

FLOYD J. METZGER. GEORGE CARL BAUER.

CERTIFICATE OF CORRECTION.

Patent No. 1, 675.123.

Granted June 26, 1928. to

FLOYD J. METZGER ET AL.

It is hereby certified that error appears in the printed specification of the b 0116 numbered patent requiring correction as follows: mlsspelled word "hydracyanic" read "hydrocyanic";

Page 1, line 66, for the page 3', line 80, claim 3, for

Z'capahe" read "capable"; page 4, line 44, claim 14, before the word "means" insert the words and comma "means for introducing solid material to the chamhcr,"; and that the said Letters Patent should he read with these corrections therein that the same may conform to the record. of the case in the Patent Office.

Signed and sealed this 21st day of August, A. D. 1928.

M. J. Moore, Acting Commissioner of lfatents.

DlSCLAlMER 1,675,123.Fl0yd J. llletzger, New York, N. Y., and George Carl Bauer, Los Angeles,

Calif. Mn'rnon or AND APPARATUS FOR FUMIGATING. Patent dated June 26,

1928. Disclaimer filed June 14, 1933, by the assignee, A'ir Reduction Company, Incorporated.

Hereby disclaims:

(a) From claims 1 to 13, inclusive, of said Letters Patent, any method of fumigating in which solid cyanide-containing material is not fed to the generating chamber and mingled with the moist gaseous medium therein.

(b) From claims 16 to 18, inclusive, of said Letters Patent, any apparatus for fumigating which does not include means for feeding solid cyanide-containing material to the generating chamber.

[Oflicial Gazette July 11, 1.933.] 

